Chlamydial ("kla-mid-ee-uhl") infection is the leading sexually
transmitted disease (STD) in the United States today, with an
estimated 4 million new cases occurring each year. Pelvic
inflammatory disease (PID), a serious complication of chlamydial
infection, has emerged as a major cause of infertility among
women of childbearing age. Chlamydial infection is caused by a
bacterium, Chlamydia trachomatis, and is transmitted during
vaginal or anal sexual contact with an infected partner. A
pregnant woman may pass the infection to her newborn during
delivery, with subsequent neonatal eye infection or pneumonia.
The annual cost of chlamydial infections and their sequelae is
estimated to exceed $2 billion.

Symptoms

Men and women with chlamydial infections may experience abnormal
genital discharge or pain during urination. These early symptoms
of chlamydial infection may be absent or very mild. If symptoms
occur, they usually appear within 1 to 3 weeks after exposure.
One of every two infected women and one of every four infected
men may have no symptoms whatsoever. As a result, the disease is
often not diagnosed until complications develop.

In women, chlamydial infections can result in PID; in men, these
infections may lead to pain or swelling in the scrotal area,
which is a sign of epididymitis, an inflammation of a part of the
male reproductive system located near the testicles. Left
untreated, this condition, like PID in women, can result in
infertility.

Chlamydial bacteria can cause proctitis (inflamed rectum) and
conjunctivitis (inflammation of the lining of the eye). The
bacteria have also been found in the throat as a result of oral
sexual contact with an infected partner. A particular strain of
chlamydia causes an uncommon STD called lymphogranuloma venereum
(LGV), which is characterized by prominent swelling and
inflammation of the lymph nodes in the groin. Complications may
follow if LGV is not treated.

Diagnosis

Chlamydial infection is easily confused with gonorrhea because
the symptoms of both diseases are similar, and they often occur
together. Until recently, the only way to diagnose chlamydial
infection was to take a sample of secretions from a patient's
genital area and attempt to grow the organism in specialized
tissue culture in the laboratory. Although still considered the
most definitive test, this method is expensive and technically
difficult, and test results are not available for up to 3 days.

Scientists have developed several rapid tests for diagnosing
chlamydial infection that use sophisticated techniques and a dye
to detect bacterial proteins. Although these tests are slightly
less accurate, they are less expensive, more rapid, and can be
performed during a routine checkup.

Treatment

A 7-day course of antibiotics such as tetracycline or doxycycline
is the recommended treatment for chlamydial infection. Other
antibiotics are effective, however, and can be used if
tetracycline cannot be taken. For example, pregnant women should
not take tetracycline, but rather can be treated with
erythromycin. Penicillin, which is often used for treating some
other STDs, is not effective against chlamydial infections. New
medications are being developed that should greatly simplify
treatment and help control the spread of chlamydia in the
population. It is very important that a person with chlamydial
infection take all of the prescribed medication, even after
symptoms disappear. To be sure that the infection is cured, a
follow-up visit to the doctor or clinic 1 to 2 weeks after
finishing the medication may be necessary. All sex partners of a
person with chlamydial infection should be evaluated and treated
to prevent re- infection and further spread of the disease.

Pelvic Inflammatory Disease

Each year up to 1 million women in the United States develop PID,
a serious infection of the reproductive organs. As many as half
of all cases of PID may be due to chlamydial infection, and many
of these occur without symptoms. PID can result in scarring of
the fallopian tubes, which can block the tubes and prevent
fertilization from taking place. An estimated 100,000 women each
year become infertile as a result of PID.

In other cases, scarring may interfere with the passage of the
fertilized egg to the uterus during pregnancy. When this
happens, the egg may implant in the fallopian tube. This is
called ectopic or tubal pregnancy. This very serious condition
results in the loss of the fetus and is a major cause of maternal
death in the United States.

Effects of Chlamydial Infection in Newborns

A baby who is exposed to chlamydial bacteria in the birth canal
during delivery may develop conjunctivitis (eye infection) or
pneumonia. Symptoms of conjunctivitis, which include discharge
and swollen eyelids, usually develop within the first 10 days of
life. Symptoms of pneumonia, including a progressively worsening
cough and congestion, most often develop within 3 to 6 weeks
after birth. Both conditions can be successfully treated with
antibiotics. However, because of these risks to the newborn,
many doctors now recommend routine testing of all pregnant women
for chlamydial infection. Prevention

Because chlamydial infection often occurs without symptoms,
people who are infected may unknowingly pass the bacteria to
their sex partners. Many doctors recommend that all persons who
have more than one sex partner, especially women under 25 years
of age, be tested for chlamydial infection regularly, even in the
absence of symptoms. Using condoms (rubbers) or diaphragms
during sexual intercourse may help reduce the transmission of
chlamydial bacteria.

Research

The development of rapid diagnostic tests for chlamydia has
marked an important breakthrough in the ability to detect
chlamydial infections. Another technique has been developed that
can detect chlamydial infection with greater accuracy than either
culture or other current tests. This test uses polymerase chain
reaction or PCR and results are available within 24 hours.
Although PCR is not yet commercially available, it is being used
in research studies and may be more widely used in the future in
referral centers. However, one of the most urgent priorities
with respect to chlamydial infection is the development of
simple, inexpensive tests for use in clinics.

Scientists are also studying the basic process of how chlamydial
bacteria cause disease in the body and why some people suffer
more severe complications than others. Animal studies have shown
that the body's immune response to the organism may be
responsible for scarring associated with chlamydial infection.
Investigators supported by the NIAID think that chlamydial
bacteria stimulate production of a number of cellular substances
that affect duration of infection and may be important in chronic
inflammation and subsequent scarring of the fallopian tubes.
These studies may lead to insights about how to prevent PID and
PID-related infertility or other complications of chlamydial
infection.

Prepared by:
Office of Communications
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, Maryland 20892

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health
Service, August 1992

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